Conducting wire, electric wire, and method for manufacturing conducting wire

Abstract

This conducting wire comprises a metallic material, and has a rectangular cross-section having a width and a thickness. Each corner portion of the rectangular cross-section is a curve, and the ratio S / SV between the area SV of a virtual rectangle circumscribing the rectangular cross-section and the area S of the rectangular cross-section is 0.975 or more. A first change rate based on the width W1 of a first cross-section and the width W2 of a second cross-section that are a predetermined length away from each other along the longitudinal axis of the conducting wire and a second change rate based on the thickness T1 of the first cross-section and the thickness T2 of the second cross-section are both 0.5% or less. The first change rate is |(W1-W2) / W1|×100, and the second change rate is |(T1-T2) / T1|×100. The arithmetic average roughness Ra of the surface of the corner portion is 0.2 μm or less.

Description

Conductor, electric wire, and method for manufacturing the same

[0001] This disclosure relates to a conductor, an electric wire, and a method for manufacturing a conductor. This application claims priority to Japanese Application No. 2022-158710, filed on September 30, 2022, and incorporates by reference all of the contents of said Japanese application.

[0002] In Patent Document 1, a conductor wire having a rectangular cross section is produced by wire drawing using multiple dies. The metal wire, which is the raw material for the conductor wire, has a circular cross section. The metal wire is gradually processed into a wire rod having an elliptical cross section, and then finished into a conductor wire having a rectangular cross section by using finishing dies.

[0003] JP 2013-4399 A

[0004] The conductor disclosed herein is a conductor made of a metal material and having a rectangular cross-section having a width and a thickness, wherein the corners of the rectangular cross-section are curved, a ratio S / SV of an area SV of an imaginary rectangle circumscribing the rectangular cross-section to an area S of the rectangular cross-section is 0.975 or greater, a first cross-section of the conductor is spaced from a second cross-section of the conductor along a longitudinal axis of the conductor, a first rate of change based on a width W1 of the first cross-section and a width W2 of the second cross-section is 0.5% or less, a second rate of change based on a thickness T1 of the first cross-section and a thickness T2 of the second cross-section is 0.5% or less, the first rate of change is |(W1-W2) / W1| × 100, the second rate of change is |(T1-T2) / T1| × 100, and the arithmetic mean roughness Ra of the surface of the corners is 0.2 μm or less.

[0005] Fig. 1 is a schematic diagram of an electric wire according to an embodiment. Fig. 2 is a cross-sectional view of a conductor provided in the electric wire shown in Fig. 1. Fig. 3 is a first explanatory diagram of a method for manufacturing a conductor according to an embodiment. Fig. 4 is a second explanatory diagram of a method for manufacturing a conductor according to an embodiment. Fig. 5 is a third explanatory diagram of a method for manufacturing a conductor according to an embodiment. Fig. 6 is a graph showing the relationship between the processing rate P of the corners and the cross-sectional area reduction rate for each sample in the test example. Fig. 7 is a graph showing the relationship between the ratio S / SV and the arithmetic mean roughness Ra of the corners for each sample in the test example.

[0006] [Problem to be Solved by the Present Disclosure] Conductors obtained by wire drawing tend to have rough corner surfaces, which can lead to defective portions where the insulating layer is insufficiently formed at the rough corners. For example, to increase the space factor of a coil, a conductor with a small radius of curvature at the corners is required. However, the smaller the radius of curvature at the corners, the more likely the corner surfaces are to become rough and the more likely the number of defective portions is to increase. An insulating layer with many defective portions may not be able to sufficiently insulate the conductor.

[0007] An object of the present disclosure is to provide a conductor in which defects in the formation of an insulating layer are less likely to occur at the corners of the rectangular cross section of the conductor.An object of the present disclosure is to provide an electric wire in which defects in the insulating layer covering the corners of the rectangular cross section of the conductor are reduced.An object of the present disclosure is to provide a method for manufacturing a conductor that can produce the conductor of the present disclosure.

[0008] Effect of the Present Disclosure The conductor of the present disclosure prevents defective portions from occurring in the insulating layer covering the corners when an insulating layer is formed around the outer periphery of the conductor.

[0009] [Description of Embodiments of the Present Disclosure] Hereinafter, embodiments of the present disclosure will be listed and described.

[0010] <1> A conductor wire according to one embodiment is a conductor wire made of a metal material, having a rectangular cross-section having a width and a thickness, wherein the corners of the rectangular cross-section are curved, a ratio S / SV of an area SV of an imaginary rectangle circumscribing the rectangular cross-section to an area S of the rectangular cross-section is 0.975 or greater, a first cross-section of the conductor wire is spaced from a second cross-section of the conductor wire along a longitudinal axis of the conductor wire, a first rate of change based on a width W1 of the first cross-section and a width W2 of the second cross-section is 0.5% or less, a second rate of change based on a thickness T1 of the first cross-section and a thickness T2 of the second cross-section is 0.5% or less, the first rate of change is |(W1-W2) / W1|×100, the second rate of change is |(T1-T2) / T1|×100, and the arithmetic mean roughness Ra of the surface of the corners is 0.2 μm or less.

[0011] A conductor wire with an S / SV ratio of 0.975 or more contributes to improving the space factor of a coil, which is the ratio of the cross-sectional area of ​​the conductor wire to the cross-sectional area of ​​the space occupied by a coil in which the conductor wire is wound.

[0012] A conductor having both a first rate of change and a second rate of change of 0.5% or less has a uniform rectangular cross-section along its longitudinal axis. The longitudinal axis of the conductor is an axis connecting the first end and the second end of the conductor along the conductor. In other words, the conductor of the present disclosure has small dimensional variation along its longitudinal axis. Products made from this conductor have reduced variation in electrical or magnetic properties. Such a conductor can be obtained by wiredrawing using a die.

[0013] When the arithmetic mean roughness Ra of the surface of the corner is 0.2 μm or less, the arithmetic mean roughness Ra of the surface of the portion other than the corner is usually about 0.02 to 0.1 μm, so the difference in arithmetic mean roughness between the corner and the portion other than the corner can be made small, and therefore, when an insulating layer is formed around the outer periphery of the conductor, defects are less likely to occur in the insulating layer covering the corner.

[0014] <2> In the conductor wire described in <1> above, the metal material may be oxygen-free copper.

[0015] Conductive wire made of oxygen-free copper has excellent conductivity. Oxygen-free copper is easy to process. Conductive wire made of oxygen-free copper has excellent weldability.

[0016] <3> In the conductor described in <1> or <2> above, the area S is 2 mm ２ Over 12mm ２ It may be the following.

[0017] 2 mm ２ Over 12mm ２ A conductor having the following area S is suitable as a material for forming a coil. The larger the area S, the larger the allowable current of the conductor.

[0018] <4> In the conductor wire according to any one of <1> to <3> above, the aspect ratio of the rectangular cross section may be 1 or more and 10 or less.

[0019] The aspect ratio is the width of a rectangular cross section divided by the thickness of the rectangular cross section. A rectangular cross section with an aspect ratio of 1 is approximately square. A conductor with a rectangular cross section whose aspect ratio is greater than 1 is known as a rectangular wire. By bending a rectangular wire edgewise, the number of turns in the coil can be increased without increasing the length of the coil along the coil axis. Rectangular wire is easy to bend flatwise. Therefore, it is easy to produce coils obtained by bending rectangular wire flatwise.

[0020] <5> In the conductor wire according to any one of <1> to <4> above, the difference between the width W1 and the width W2 and the difference between the thickness T1 and the thickness T2 may both be 16 μm or less.

[0021] The conductor <5> has a uniform rectangular cross section along its longitudinal axis. Therefore, the conductor <5> reduces variations in performance between turns in a coil made from this conductor. This conductor allows for the mass production of coils that exhibit stable performance.

[0022] <6> An electric wire according to the embodiment includes the conductor wire according to any one of <1> to <5> above, and an insulating layer covering a surface of the conductor wire.

[0023] An electric wire comprising a conductor and an insulating layer can be used, for example, as a material for a coil. Because the corners of the conductor are smooth, defects are less likely to form in the insulating layer covering the corners. Using such an electric wire, a coil with stable performance can be manufactured.

[0024] <7> A method of manufacturing a conductor according to an embodiment includes a step of final wiredrawing a raw material wire, the raw material wire being a metal wire immediately prior to the final wiredrawing step, the cross section of the raw material wire having four corners, the cross section having a width W0, a thickness T0, and a diagonal length L0, the rectangular cross section having a width W, a thickness T, and a diagonal length L, a processing ratio P of the corners in the final wiredrawing is 20% or more, the processing ratio P is {(L0-L) / X}×100, where X is the larger of W0-W and T0-T, and a cross-sectional area reduction rate in the final wiredrawing is 35% or less.

[0025] The final wiredrawing process is a so-called finish wiredrawing process. If the cross-sectional area reduction rate in the final wiredrawing process is 35% or less, the conductor wire is less likely to break. As the cross-sectional area reduction rate decreases, the drawing force required to pull the raw wire through the die decreases, and the stress acting on the raw wire decreases. However, in a wiredrawing process with a small cross-sectional area reduction rate, the contact area between the die and the raw wire decreases, and the stress per unit area acting on the surface of the raw wire, i.e., the surface pressure, increases. If the surface pressure acting on the raw wire during wiredrawing increases, the surface of the conductor wire, including the corners, tends to become smooth. Furthermore, if the processing ratio P in the final wiredrawing process is 20% or more, the corners of the raw wire are sufficiently processed, resulting in a smooth surface at the corners of the conductor wire. As a result, a conductor wire having corners with a surface having an arithmetic mean roughness Ra of 0.2 μm or less is obtained.

[0026] [Details of the Embodiments of the Present Disclosure] Specific examples of conductors according to embodiments of the present disclosure, methods for manufacturing such conductors, and electric wires including such conductors will be described below with reference to the drawings. The same reference numerals in the figures indicate the same or corresponding parts. The dimensions of components shown in the drawings are expressed for the purpose of clarity and do not necessarily represent actual dimensions. The present invention is not limited to these examples, but is defined by the claims, and all modifications within the meaning and scope of the claims are intended to be included.

[0027] <Embodiment 1> <Electric Wire> The electric wire 1 shown in Fig. 1 includes a conductor 2 made of a metal material and an insulating layer 3 covering the surface of the conductor 2. As shown in Fig. 2, the conductor 2 has a rectangular cross section 20. The rectangular cross section 20 is a cross section of the conductor 2 cut along a plane perpendicular to the longitudinal axis of the conductor 2. The conductor 2 has a substantially uniform rectangular cross section 20 along the longitudinal axis of the conductor 2.

[0028] [Conductive Wire] The metal material constituting the conductive wire 2 is, for example, copper, copper alloy, aluminum, or aluminum alloy. These metal materials are relatively inexpensive and have excellent conductivity. In particular, the conductive wire 2 made of oxygen-free copper has excellent conductivity. Oxygen-free copper is pure copper containing 99.95% by mass or more of copper, with the remainder being unavoidable impurities. The total content of unavoidable impurities in oxygen-free copper is, for example, 0.03% by mass or less. The oxygen content in oxygen-free copper is, for example, 0.005% by mass (50 ppm by mass) or less, further 0.002% by mass (20 ppm by mass) or less, and further 0.001% by mass (10 ppm by mass) or less. The lower the oxygen content in oxygen-free copper, the higher the conductivity of the oxygen-free copper.

[0029] Corners 29 of rectangular cross section 20 are curved. The ratio S / SV of the area SV of imaginary rectangle 25 circumscribing rectangular cross section 20 to the area S of rectangular cross section 20 is 0.975 or greater. Areas S and SV are determined from a micrograph of rectangular cross section 20. Specifically, the micrograph of rectangular cross section 20 is subjected to image analysis to identify the outer contour of rectangular cross section 20. The area enclosed by this outer contour is area S. Imaginary rectangle 25 indicated by a two-dot chain line in FIG. 2 is the smallest rectangle circumscribing the outer contour of rectangular cross section 20 in the micrograph of rectangular cross section 20. The area inside imaginary rectangle 25 in the micrograph is area SV. A conductor with a ratio S / SV of 0.975 or greater contributes to improving the space factor of a coil. The space factor is the ratio of the cross-sectional area of ​​conductor 2 to the cross-sectional area of ​​the space occupied by a coil in which conductor 2 is wound. The higher the ratio S / SV, the higher the space factor. To improve the space factor, the ratio S / SV may be set to, for example, 0.990 or more, or even 0.995 or more.

[0030] The area S of the rectangular cross section 20 is, for example, 2 mm ２ Over 12mm ２ Less than 2 mm ２ Over 12mm ２ The conductor 2 having the following area S can be used as a material for forming the coil. The larger the area S, the larger the allowable current of the conductor 2. For example, the area S is 3 mm ２ More than 10 mm ２ It can be less than 5mm ２More than 10 mm ２ The following is also fine.

[0031] The corners 29 are arc-shaped. The radius of curvature of the arc-shaped corners 29 is, for example, 0.07 mm or more and 0.50 mm or less. Corners 29 with a radius of curvature of 0.07 mm or more are not too sharp and therefore are less likely to be damaged. In addition, the insulating layer 3 formed on the outer periphery of the not-too-sharp corners 29 is also less likely to be damaged. If the radius of curvature of the corners 29 is 0.50 mm or less, the area SV of the rectangular cross section 20 does not become too small. The radius of curvature may be, for example, 0.09 mm or more and 0.40 mm or less, 0.10 mm or more and 0.25 mm or less, or 0.10 mm or more and 0.15 mm or less.

[0032] The rectangular cross section 20 has a width W and a thickness T. The width W of the rectangular cross section 20 is equal to the length of a first side 251 of the imaginary rectangle 25. The thickness of the rectangular cross section 20 is equal to the length of a second side 252 of the imaginary rectangle 25 that is perpendicular to the first side 251. The width W and the thickness T may be the same or different. In this example, the width W is longer than the thickness T. A conductor 2 having a different width W and thickness T is a so-called rectangular wire.

[0033] In the conductor 2, a first cross section 21 and a second cross section 22 spaced apart along the longitudinal axis of the conductor 2 have almost the same shape and dimensions. The first cross section 21 is a rectangular cross section 20 at the position of arrow A in Figure 1. The second cross section 22 is a rectangular cross section 20 at the position of arrow B in Figure 1. The distance between arrows A and B in Figure 1 is short for the sake of convenience. The distance between the first cross section 21 and the second cross section 22 is, for example, 100 m.

[0034] A first rate of change based on the width W1 of the first cross section 21 and the width W2 of the second cross section 22 is 0.5% (percent) or less, and a second rate of change based on the thickness T1 of the first cross section 21 and the thickness T2 of the second cross section 22 is 0.5% or less. First rate of change...|(W1-W2) / W1|×100 Second rate of change...|(T1-T2) / T1|×100

[0035] A conductor 2 in which the first rate of change and the second rate of change are both 0.5% or less has a rectangular cross section 20 that is substantially uniform along the longitudinal axis of the conductor 2. Wire drawing using a die can produce a conductor 2 with small dimensional variation along the longitudinal axis of the conductor 2. Therefore, a conductor 2 in which the first rate of change and the second rate of change are both 0.5% or less can be said to have been obtained by wire drawing using a die. The first rate of change and the second rate of change may each be 0.4% or less, or 0.2% or less.

[0036] Conductor 2 having a uniform rectangular cross section 20 along the longitudinal axis of conductor 2 reduces variations in performance between turns in a coil made from conductor 2. Conductor 2 allows for mass production of coils that exhibit stable performance.

[0037] The dimensional variation along the longitudinal axis of the conductor 2 may be evaluated in absolute values. For example, the difference W1-W2 between the width W1 of the first cross section 21 and the width W2 of the second cross section 22 may be 16 μm or less, and the difference T1-T2 between the thickness T1 of the first cross section 21 and the thickness T2 of the second cross section 22 may be 16 μm or less. The smaller the differences W1-W2 and T1-T2, the more the variation in performance of each turn in a coil made from the conductor 2 is suppressed. The differences W1-W2 and T1-T2 may be, for example, 12 μm or less, or 8 μm or less.

[0038] The surfaces of the corners 29 of the conductor 2 are very smooth. Specifically, the arithmetic mean roughness Ra of the surfaces of the corners 29 is 0.2 μm or less. In this example, the arithmetic mean roughness Ra is the average of measurement results obtained by measuring at three locations on each of the four corners 29. In other words, the arithmetic mean roughness Ra is the average of measurement results obtained at 12 locations. The arithmetic mean roughness Ra in this example conforms to JIS B 0601:2013. The arithmetic mean roughness Ra can be determined, for example, using a commercially available non-contact roughness measuring device, specifically, the LEXT OLS4100 manufactured by Olympus Corporation.

[0039] The surface of the corner 29, which has the arithmetic mean roughness Ra, is as smooth as the surface of the portion other than the corner 29. Therefore, when the insulating layer 3 is formed around the outer periphery of the conductor 2, defects are unlikely to occur in the insulating layer 3 covering the corner 29. The arithmetic mean roughness Ra may be, for example, 0.15 μm or less, 0.1 μm or less, or 0.08 μm or less.

[0040] [Insulating Layer] The insulating layer 3 ensures insulation of the conductor 2. The insulating layer 3 is, for example, enamel formed by solidifying insulating varnish. Alternatively, the insulating layer 3 may be made of a resin with high electrical insulation properties, such as polyimide resin, fluororesin, polyethersulfone, or polyetheretherketone.

[0041] The thickness of the insulating layer 3 may be, for example, 1 μm or more and 100 μm or less, or 10 μm or more and 50 μm or less. Here, the corners 29 of the conductor 2 in this example are very smooth, and defects are unlikely to occur in the insulating layer 3 formed around the smooth corners 29. Therefore, even if the thickness of the insulating layer 3 is within the above range, defects are unlikely to occur in the insulating layer 3. The insulating layer 3 covers part or all of the surface of the conductor 2.

[0042] <<Method for manufacturing electric wire>> The method for manufacturing electric wire 1 includes a step of obtaining conductor wire 2 by wiredrawing a metal wire, a step of heat-treating conductor wire 2, and a step of forming insulating layer 3 on the outer periphery of conductor wire 2 after heat treatment.

[0043] [Process for Obtaining Conductive Wire] The conductive wire 2 is obtained, for example, by the conductive wire manufacturing method of the present disclosure. The conductive wire manufacturing method in this example is performed by a wire drawing device 6 shown in FIG. 3. The wire drawing device 6 includes, for example, a plurality of dies 61, 62, 63, and 64. By passing the metal wire 9 through the dies 61, 62, 63, and 64, the metal wire 9 can gradually approach the desired shape and wire diameter. At least the die 64 is a wire drawing die. The dies 61, 62, and 63 may be roller dies.

[0044] One of the features of the method for manufacturing the conductor wire 2 is that processing under predetermined conditions is performed in the final drawing in the wire drawing device 6. The characteristic features of the method for manufacturing the conductor wire 2 will be described below with reference to Fig. 4. In this description, the metal wire 9 that is fed to the final die 64 is referred to as the raw wire 4.

[0045] 4, the solid line indicates the cross section of the raw wire 4. The two-dot chain line indicates the cross section of the conductor 2 obtained by drawing the raw wire 4. Hatching is omitted in FIG. 4 for ease of explanation.

[0046] The raw wire 4 has a cross section 40 having four corners 49. The cross section 40 is a cross section of the raw wire 4 cut along a plane perpendicular to the longitudinal axis of the raw wire 4. In this example, the cross section 40 has a shape that is vertically and horizontally symmetrical. The corners 49 may have a pointed shape formed by connecting two straight lines, or may be curved. In this example, the corners 49 are curved. The contour line connecting two adjacent corners 49 along the periphery of the cross section may be straight, or may be a curve that convex in a direction away from the center of the cross section. In this example, the contour line is straight. The cross section 40 has a width W0 and a thickness T0. The width W0 and thickness T0 are the same as the lengths of the first and second sides, respectively, of an imaginary rectangle circumscribing the cross section 40. The first and second sides are two sides that intersect at right angles to each other. The width W0 and thickness T0 may be the same or different. In this example, the width W0 is longer than the thickness T0. The corners 49 are, for example, portions from both ends of the first side that correspond to 10% of the total length of the first side. The corners 49 are, for example, portions from both ends of the second side that correspond to 10% of the total length of the second side.

[0047] The method for manufacturing the conductor 2 includes a step of drawing the raw wire 4 to obtain the conductor 2 having a rectangular cross section 20. As already described, the rectangular cross section 20 has a width W and a thickness T. The outline of the rectangular cross section 20 in FIG. 4 can be considered to substantially match the outline of the portion of the die hole of the die 64 (FIG. 3) that has the smallest inner diameter, i.e., the outline of the bearing of the die 64. The rectangular cross section 20 has a shape that is symmetrical both vertically and horizontally.

[0048] The cross-sectional area reduction rate in the final wiredrawing process is 35% or less. More preferably, the cross-sectional area reduction rate is 15% or more and 35% or less. The cross-sectional area reduction rate is an index showing how much the area S of the rectangular cross section 20 is reduced relative to the area S0 of the cross section 40. Specifically, the cross-sectional area reduction rate is calculated by {(S0 - S) / S0} x 100. If the cross-sectional area reduction rate in the final wiredrawing process is 35% or less, the surface of the corner 29 will be smooth. The die 64 may be an angle-type die, a circular-type die, or a hybrid die. As shown in Figure 5, an angle-type die is a die in which the shape of the approach 641 of the die 64 in the longitudinal cross section is linear. An arc-type die is a die in which the shape of the approach is curved. A hybrid die is a die in which the shape of the approach is a combination of straight and curved lines. The approach angle θ of the die 64 may be constant or may vary at different positions on the approach. A high approach angle θ is desirable to increase the degree of processing of the surface of the raw wire 4. As shown in FIG. 5 , the approach 641 is a tapered portion located on the entrance side of a bearing 642, which is a hole inside the die that determines the dimensions of the conductor 2, and has the function of narrowing the outer diameter of the raw wire 4. The approach angle θ is the angle formed by the tapered approach 641 in the vertical cross section of the die 64, and is the sum of the angle formed at the top and the angle formed at the bottom with respect to the horizontal.

[0049] The processing rate P of the corners 49 in the wire drawing is 20% or more. The processing rate P of the corners 49 is an index showing whether the corners 49 are significantly deformed when the raw wire 4 is drawn. Specifically, the processing rate P is calculated by {(L0-L) / X} x 100. L0...diagonal length of the cross section 40 of the raw wire 4 L...diagonal length of the rectangular cross section 20 of the conductor 2 X...maximum deformation amount of the portion other than the corners 49

[0050] The diagonal length L is the length of the diagonal of the rectangular cross section 20, i.e., the distance between the first corner 29 and the second corner 29, which are located at diagonal positions on the rectangular cross section 20. When the corner 29 is arc-shaped as in this example, the straight line connecting the midpoint of the first arc and the midpoint of the second arc is the diagonal of the rectangular cross section 20. On the other hand, the diagonal length L0 is the length of the diagonal of the cross section 40. In this example, the straight line connecting the first intersection point and the second intersection point on the cross section 40 is the diagonal of the cross section 40. The first intersection point and the second intersection point are the intersection points between the extension of the diagonal of the rectangular cross section 20 and the contour line of the cross section 40, respectively. The value obtained by subtracting the diagonal length L from the diagonal length L0 can be considered to be the deformation amount of the corner 49 due to the final wiredrawing process.

[0051] The maximum deformation amount X is the larger of W0-W and T0-T. The width W and thickness T are approximately the same as the dimensions of the portion of the die hole of the die 64 having the smallest inner diameter. In the conventional final wiredrawing process, the corners 49 are hardly deformed, and the portions other than the corners 49 are largely deformed. That is, in the conventional final wiredrawing process, the maximum deformation amount X is significantly larger than the deformation amount L0-L of the corners 49.

[0052] In this example, the processing ratio P is 20% or more. By performing the final wiredrawing process with such a processing ratio P, the corners 49 are processed as thoroughly as the other parts, and the surfaces of the corners 29 become as smooth as the other parts. As a result, a conductor 2 is obtained that includes corners 29 having a surface with an arithmetic mean roughness Ra of 0.2 μm or less. The larger the processing ratio P, the higher the processing degree of the corners 49, and the smoother the surfaces of the corners 29 become. The processing ratio P may be, for example, 30% or more, 45% or more, or 60% or more.

[0053] [Process for Heat Treating Conductive Wire] The main purpose of the heat treatment performed after the final drawing is to remove strain introduced into the conductor wire 2 by the drawing process. Removal of strain improves the electrical conductivity and elongation of the conductor wire 2. The atmospheric temperature in the heat treatment is, for example, about 100°C or higher and 550°C or lower, and the holding time is, for example, 0.2 seconds or higher and 10 hours or lower. The heat treatment may be performed in a batch furnace or a continuous furnace. This heat treatment is not essential.

[0054] [Step of Forming the Insulating Layer] The insulating layer 3 is formed, for example, by known enameled wire coating equipment. The coating equipment performs a first step of applying a resin that will form the insulating layer 3 to the surface of the conductor wire 2, and a second step of solidifying the resin applied to the conductor wire 2 in a baking oven. The first and second steps are repeated until the insulating layer 3 reaches a desired thickness. Each of the first and second steps may be performed once.

[0055] <Test Example> In the test example, a plurality of conductors 2 were produced with different cross-sectional area reduction rates and different processing ratios P ​​of corners 49 in the final wiredrawing process. The die 64 used in the final wiredrawing process to produce each conductor 2 was an angle die or an arc die. Next, an insulating layer 3 was formed on the outer periphery of each conductor 2, and defects in the insulating layer 3 were confirmed. The wiredrawing conditions and the dimensions of the conductors 2 are shown in Tables 1 and 2.

[0056] The "Die Hole Dimensions" in the table refer to the dimension of the portion of the die hole of the die 64 with the smallest inner diameter, i.e., the dimension of the bearing of the die 64. The dimension of the bearing is approximately equal to the dimension of the rectangular cross section 20 of the conductor 2. Therefore, the "Thickness," "Width," "Corner Curvature Radius," and "Area" listed in the "Die Hole Dimensions" column can be considered to be the "Thickness T," "Width W," "Corner Curvature Radius 29," and "Area S of the Rectangular Cross Section 20" in FIG. 4, respectively. The "Aspect Ratio" is "Width / Thickness."

[0057] The "degree of pre-working" in the "final wiredrawing conditions" column in the table indicates the amount of processing applied to the metal wire 9 after the last heat treatment and before the final wiredrawing, expressed as a percentage. Specifically, the "degree of pre-working" is {(S9 - S0) / S9} x 100. S9 is the cross-sectional area of ​​the metal wire 9 immediately before being subjected to the wiredrawing device 6, i.e., the cross-sectional area of ​​the metal wire 9 immediately before the die 61. S0 is the cross-sectional area of ​​the cross section 40 of the raw wire 4, i.e., the cross-sectional area of ​​the metal wire 9 immediately before the die 64. "T0 - T", "W0 - W", "L0 - L", and "corner processing ratio P" are as explained in the above section [Method for manufacturing a conductor wire].

[0058] The "S / SV ratio" in the "Conductor" column in the table is as explained in the section [Conductor] above. The area S and area SV were determined by image analysis of cross-sectional images of the conductor 2 taken with a VHX-7000 manufactured by Keyence Corporation. The "S / SV ratio" in the table is expressed as a percentage. "Dimensional uniformity" is the result of evaluating whether the conductor 2 has a uniform rectangular cross-section 20 along its longitudinal axis. A rating of "A" means that the "first rate of change" and "second rate of change," as explained in the section [Conductor], are both 0.5% or less. The distance between the first cross-section 21 and the second cross-section 22 used to measure the "first rate of change" and "second rate of change" was 100 m.

[0059] "Corner Ra" in the table refers to the arithmetic mean roughness Ra of the surface of the corner 29 of the conductor 2. The unit of arithmetic mean roughness is micrometers. The arithmetic mean roughness Ra was measured using a LEXT OLS4100 manufactured by Olympus Corporation. Specifically, the arithmetic mean roughness Ra was measured at three locations on each of the four corners 29, and the arithmetic mean roughness Ra was calculated by averaging the 12 measurement results. The three measurement locations on each corner 29 were spaced apart from one another along the arc of the corner 29. In this example, each measurement location was measured over a length of 258 μm along the longitudinal axis of the conductor 2.

[0060] The "Defective Point Occurrence Rate" in the table refers to the number of defective points in the insulating layer 3 for a 100 kg conductor 2. In this example, the defective points in the insulating layer 3 were measured using a commercially available flaw detector. If the surface of the conductor 2 is rough, defects such as air pockets will occur between the roughened portion and the insulating layer 3. In this example, a commercially available flaw detector was installed next to the coating equipment for the insulating layer 3, and the number of defective points was counted immediately after the insulating layer 3 was formed. The weight of the conductor 2 was calculated from the specific gravity of the material of the conductor 2, the area S of the rectangular cross section 20, and the feed speed of the conductor 2 in the coating equipment. In this example, of the measured defective points, only the defective points corresponding to the corners 29 were counted.

[0061] Samples No. 1 to No. 15 differ primarily in the cross-sectional area reduction rate. Die 64 was an angled die with an approach angle of 32°. Samples No. 21 to No. 24 differ primarily in the radius of curvature of the corner 29 of the conductor 2. Die 64 was an angled die with an approach angle of 32°. Samples No. 31 to No. 33 differ primarily in the aspect ratio. Die 64 was an angled die with an approach angle of 32°. Samples No. 41 and No. 42 differ primarily in the area S of the rectangular cross section 20 of the conductor 2. Die 64 was an angled die with an approach angle of 32°. Samples No. 51 to No. 56 differ primarily in either the thickness T or the width W of the rectangular cross section 20. Die 64 was an angle-type die with an approach angle of 32°. Samples No. 61 to 64 were samples with different die 64 configurations. Die 64 of Sample No. 61 was an angle-type die with an approach angle of 24°. Die 64 of Sample No. 62 was an angle-type die with an approach angle of 16°. Die 64 of Sample No. 63 was an arc-type die with an arc-shaped approach with a curvature radius of 6 mm. Die 64 of Sample No. 64 was an arc-type die with an approach with a curvature radius of 12 mm. Samples No. 101 to 104 were samples in which the processing ratio P of the corner portion 29 was less than 20% or the cross-sectional area reduction rate was more than 35%. Die 64 was an angle-type die with an approach angle of 32°.

[0062]

[0063]

[0064] As shown in Tables 1 and 2, Samples No. 1 to 64, in which the cross-sectional area reduction rate was 35% or less and the processing rate P of the corner portion 49 was 20% or more, had smooth corner portions 29 and the incidence rate of defective portions was 0.8 or less.

[0065] Samples No. 101 to 103, in which the processing ratio P of the corner portion 49 was less than 20%, had corner portions 29 with an arithmetic mean roughness Ra of more than 0.2 μm, and the incidence of defective portions was more than 1.2. Also, sample No. 104, in which the cross-sectional area reduction rate was more than 35%, had corner portions 29 with an arithmetic mean roughness Ra of more than 0.2 μm, and the incidence of defective portions was more than 1.0.

[0066] FIG. 6 is a graph showing the relationship between the processing rate P of the corner portion 49 and the cross-sectional area reduction rate for each sample in the test example. The horizontal axis represents the processing rate P of the corner portion 49 for each sample. The vertical axis represents the cross-sectional area reduction rate for each sample. As shown in Table 2, samples No. 101 to No. 104 are samples with a high incidence of defective portions. The samples in the range excluding samples No. 101 to No. 104 are samples with a low incidence of defective portions. Therefore, it is considered that the incidence of defective portions is low when the processing rate P of the corner portion 49 is in the range of 20% to 140% and the cross-sectional area reduction rate is in the range of 7% to 35%. It is considered that the incidence of defective portions is even lower when the processing rate P of the corner portion 49 is in the range of 20% to 140% and the cross-sectional area reduction rate is in the range of 15% to 35%. It is believed that the rate of occurrence of defective portions is even lower when the processing rate P of the corner portion 49 is in the range of 40% to 140% and the cross-sectional area reduction rate is in the range of 15% to 35%.

[0067] FIG. 7 is a graph showing the relationship between the S / SV ratio and the arithmetic mean roughness Ra of the corners for each test sample. The horizontal axis represents the S / SV ratio for each sample. The vertical axis represents the arithmetic mean roughness Ra of the corners 29. The closer the S / SV ratio is to 100%, the smaller the radius of curvature of the corners 29, i.e., the more pointed the corners 29 are. The closer the S / SV ratio is to 100%, the more pointed the corners 29 are, making it more difficult to smooth the surfaces of the corners 29. However, the arithmetic mean roughness Ra of the corners 29 of Samples 1 to 64, which satisfied the cross-sectional area reduction rate and processing ratio P shown in FIG. 6, was 0.2 μm or less. Therefore, it can be said that the manufacturing method of the conductive wire 2 according to the embodiment is effective in forming corners 29 with smooth surfaces.

[0068] REFERENCE SIGNS LIST 1 Electric wire 2 Conductor 20 Rectangular cross section 21 First cross section 22 Second cross section 25 Virtual rectangle 251 First side 252 Second side 29 Corner 3 Insulating layer 4 Raw wire rod 40 Cross section 49 Corner 6 Wire drawing device 61, 62, 63, 64 Die 641 Approach 642 Bearing 9 Metal wire θ Approach angle T, T0, T1, T2 Thickness W, W0, W1, W2 Width

Claims

1. A conductor made of a metal material, a rectangular cross-section having a width and a thickness; The corners of the rectangular cross section are curved, a ratio S / SV of an area SV of a virtual rectangle circumscribing the rectangular cross section to an area S of the rectangular cross section is 0.975 or more; the first cross-section of the conductor is spaced from the second cross-section of the conductor along a longitudinal axis of the conductor; a first rate of change based on the width W1 of the first cross section and the width W2 of the second cross section is 0.5% or less; a second rate of change based on the thickness T1 of the first cross section and the thickness T2 of the second cross section is 0.5% or less; the first rate of change is |(W1-W2) / W1|×100, the second rate of change is |(T1-T2) / T1|×100, The arithmetic average roughness Ra of the surface of the corner is 0.2 μm or less. Conductor.

2. The lead of claim 1 , wherein the metallic material is oxygen-free copper.

3. The area S is 2 mm ２ More than 12mm ２ 3. The conductor according to claim 1 or 2, wherein:

4. The conductor according to claim 1 or 2, wherein the aspect ratio of the rectangular cross section is 1 or more and 10 or less.

5. 3. The conductor according to claim 1, wherein the difference between said width W1 and said width W2 and the difference between said thickness T1 and said thickness T2 are both 16 μm or less.

6. The conductor according to claim 1 or 2; and an insulating layer covering the surface of the conductor. Electric wire.

7. 1. A method for producing a conductor to obtain a conductor having a rectangular cross section, comprising the steps of: The process includes a final wire drawing process for the raw wire material. The raw wire rod is a metal wire immediately before the final wiredrawing process, The cross section of the raw wire has four corners, The cross-section has a width W0, a thickness T0, and a diagonal length L0; The rectangular cross section has a width W, a thickness T, and a diagonal length L; The processing ratio P of the corner portion in the final wiredrawing process is 20% or more, The processing ratio P is {(L0-L) / X}×100, where X is the larger of W0-W and T0-T. The cross-sectional area reduction rate in the final wiredrawing process is 35% or less. A method for manufacturing conductor wire.